Self-modulating gas burner

ABSTRACT

An automatic, self-modulating, gas-fired, gas-powered, forcedcirculation residential or other hot water heating system, which is fully and efficiently operable without electricity or any other form of externally supplied power, other than the natural or other gas used for combustion, and includes a zone temperature-responsive control system which likewise requires no electricity or other external source of power.

United States Patent lnventor Walton W. Cushman 36483 Gloucester Drive,Fraser, Mich. 48026 Appl. No. 8,901

Division of Ser. No. 714,649, Mar. 20, 1968, Pat. No. 3,514,034

Filed Feb. 5, 1970 Patented Aug. 17, 1971 SELF-MODULATING GAS BURNER 6Claims, 8 Drawing Figs.

0.8. CI 137/252, 137/609, 236/50 Int. Cl Fl6k 9/00 Field ofSeareh236/l,50; 431/89, 90

References Cited UNITED STATES PATENTS 1,576,086 3/1926 Browne...236/50UX 2,362,045 11/1944 Bliss 236/1EUX 2,390,806 12 1945 Nagel 2361EUX 3,062,271 11/1962 Rijnsdorp 431 90x Primary Examiner- Edward J.Michael Attorney-Lon H. Romanski ABSTRACT: 'An automatic,self-modulating, gas-fired, gaspowered, forced-circulation residentialor other hot water heating system, which is fully and efi'icientlyoperable without electricity or any other form of externally suppliedpower, other than the natural or other gas used for combustion, andincludes a zone temperature-responsive control system which likewiserequires no electricity or other external source of power.

PATENTED MIG] Han SHEET 2 BF 3 INVENTOR. m; 70 m cw/m m/v JTTOR/VEYSELF-MODULATING GAS BURNER RELATED APPLICATION This application is adivision of my copending application Ser. No. 714,649 filed Mar. 20,1968, entitled GAS-FIRED BRIEF SUMMARY OF THE INVENTION This inventionrelates generally to hot water heating systems, and more particularly tosuch systems wherein any suitable gaseous fuel is fired in a combustionchamber associated with a hot water boiler construction wherein thetemperature of the water is substantially elevated prior to its beingforce-circulated within a substantially closed system to thermalradiation devices where most of the heat is released prior to its returnto the boiler assembly for reheating and recirculation.

In most such installations, current practice requires the use of one ormore electrically or otherwise mechanically driven pumps to provide thenecessary hotwater circulation, along with some form ofelectromechanical or electrothermal valving or zone circuitry andgas-burner control, including certain safety controls. This inventioncontemplates the complete elimination of theneed for electricity as asource of power, either for hot water circulation or to activate thecontrol system.

Further, most systems currently used are designed to operate on acharacteristic ON-OFF" cycle. That is, when the thermostat or otherthermally sensitive element cools, it closes an electrical circuitwhich,in most cases, simultaneously or sequentially actuates the gas burner,the circulating pump, and a valve for the zone or zones to be heated.Since the water in the radiation system served by this particularthermostat has very likely already lost all or most of its heat, thesudden inrush of hot water from the boiler often results in considerableundesirable noise caused by the expansion of the pipes, and'otherelements of the radiationsystem.

This invention reduces or eliminates the noise problem inthat itcontemplates that both the circulatory system and its correspondinggas-burner system are modulated so as to eliminate this characteristicON-OFF cycle. That is, instead of cycling between ON and OFF, theproposed system automatically and simultaneously modulates-both the gasflame and the rate of water circulation to substantially match the heatloss requirements of the zone affected. If, forfexample, the outsideambient is such that a conventional system would be ON fora period andthen'OFF for a period, the system of this invention would automaticallyselect an intermediate flame or gas consumption rate, along'with acorresponding intermediate hot water circulatory rate, and operate so"as to make only infinitely small corrections of increase or decrease ineach rate as required. Such operation not only virtually eliminates allthermally induced noise, but it also substantially increases the overallthermalefficiency.

From the standpoint of operating economies, there is probably nothingquite so wasteful as a system requiring repetitious OFF and ON cycles,with its corresponding relatively cold firebox, followed by a highlycontrasting very hot firebox and its inescapable overdrafting. Thelatter condition continues for a considerable period of time after thestart of an OFF cycle because the stack temperature is so high that itcauses the interior air to be drawn up and out for's'everal minutesafter combustion has completely stopped. Not only does this remove 'asubstantial portion of the alre'adyheated room temperature air fromwithin the structure,but it also excessively cools the boiler and stackat a very rapid rate, ejecting the'now overheated air to the outsideatmosphere through the chimney. At the same time, a condition is created'such that reasonably proper combustion cannot again get underway untilthe next ON cycle has been in operation long enough for the fire boxtemperature to come up to efiicient operating temperatures, which is thereason that most heating engineers recommend against an installationwith a total heat capacity that is even slightly over and above thatwhich is absolutely required on the coldest day that can be anticipated.

It is known that continuous, uninterrupted operation of conventionalheating systems will provide maximum fuel economies, particularly onthose relatively infrequent very cold and windy days when the systemmust operate continuously to just barely replace the heat lost. Such anengineering compromise is of very little value, however, during thosemilder portions of the heating season when the heating system, becauseit is essentially too large for such moderate weather, must necessarilycycle between ON and OFF, and it is of small comfort to thoseindividuals who would prefer to have at least some margin of safety forthe unpredictable, record-breaking, ultra-cold and windy day.

Equally important, it is not at all unusual for a conventional heatingsystem to break down or fail for any number of reasons, including anelectrical power or component failure. At such times, the building orother structure rapidly loses much of its heat, and, only when thesystem has been repaired and restarted, it is often discovered that thesystem may be unable, even when operating at continuous full outputcapacity for a reasonable period of time, to replace all the heat lostduring the earlier shutdown period. By completely eliminating theelectrical system, the invention eliminates virtually all of the majorand most frequent causes of failure in heating systems, includingfailures in both the source of the electricity and in the manyelectrically driven or electrically activated components of existingconventional systems.

Another important problem associated with conventional heating systemsis the matter or personal comfort due to the excessive (some averageabout 3.5 F.) temperature differential required to cycle the thermostat.When the temperature in a zone must be raised 3.5 F. above thetemperature where it last came ON before recycling the heating system toOFF, the result is not only exceedingly uncomfortable, but it is alsowasteful. It will be seen that the control apparatus of this inventionis capable of holding the temperature variation of a given closed areato less than plus or minus 0. 1 F.

There are, of course, other problems and disadvantages with conventionalgas-fired, hot water heating systems, and a main object of the inventionis to provide such a system that is capable of operation by thecombustion gas alone, totally independent of electricity or othermechanical sources of power, either for circulation or automaticcontrol.

Another object of the invention is to provide such a system having twoprinciple circuits, a gas circuit and a water circuit, the gas circuitproviding the power for automatic control of water circulation.

Another object of the invention is to provide such a system wherein thewater is force-circulated by the compression energy contained in thecombustion gas.

Still another object of the invention is to provide such a systemwherein the heating capability of the water heating element isautomatically modulated to substantially match the heat loss of the areaor zone being heated.

Another object of the invention is to provide such a system wherein thewater circulation rate is automatically modulated to substantially matchthe heat balance between the water heating element and the heatradiating elements.

Another object of the invention is to provide such a system whereinheated water circulation is accomplished by a gas-lift water pumpprovided by cooperative action between the gas and water circuits.

Another object of the invention is to provide a novel gas-lift waterpump construction.

Still another object of the invention is to provide such a system havingmeans for automatically modulating the combustion gas pressure to theburner.

Another object of the invention is to provide a novel closed pressuremodulation means for accuratelysensing and controlling the heated zonetemperature.

Another object of the invention is to provide such a system wherein thegas pressure modulating means operates on a balance between a primaryzone temperature responsive pressure and a secondary, adjustable,gravity-induced, heavyliquid pressure to control a gas pressure controlvalve.

A further object of the invention is to provide a novel gas pressureand/or flow control valve.

A still further object of the invention is to provide such a systemwherein the modulated gas pressure and/or flow is effective to modulatethe water circulation rate.

A further object of the invention is to provide such a system having anovel self-modulating gas burner construction.

A still further object of the invention is to provide such a systemwherein modulation of the gas pressure and/or flow affects automaticmodulation of the burner.

Another object of the invention is to provide such a system that isautomatically self-modulating so as to provide substantially infinitelyvariable or stepless heat gradients, eliminating thermally'inducednoise, shock and vibration, as well as inefficiencies due to widelyvarying stack and combustion chamber temperature and/or inadequate orexcessive drafting.

I Still another object of the invention is to provide such a systemcapable of highly consistent and stable temperature and comfort control.

Another equally important object of the invention is to provide such asystemthat is dependable, efficient and less expensive to manufacture,install, and operate.-

Another object of the invention is to provide sucha system that requiresessentially zero maintenance of any kind, except as might be required torepair physical damage resulting from abnormal causes not related tooperation of the system.

These and other objects and advantages of the invention will-becomereadily apparent upon references to the followin detailed descriptionand the attached drawings.

BRIEF DESCRIPTION OF THE VARIOUS VIEWS OF THE DRAWINGS FIG. 1 is adiagrammatic illustration of a heating system embodying the invention. I

FIG. 2 is an enlarged schematic elevational view illustratin the heated'zone temperature control and modulated gas supply'portion of the systemshown by FIG. 1.

FIG. 3is an enlarged top plan vie of a portion of FIG. 2.

FIG. 4 is an enlarged cross-sectional view of a portion of FIG. 2. v v

FIG. 5 is an enlarged cross-sectional view of a portion of FIG. 3. v

FIG. 6 is an enlarged schematic elevational view of the water heatingburner and gas-lift, forced-circulation pump portion of the system shownby FIG. 1.

FIG. 7 is an enlarged cross-sectional view taken on the plane of line7-7 of FIG. 6, looking in the direction of the arrows.

FIG. 8 is an enlarged side elevational view, with portions thereofbroken away and in cross section, of the automatically self-modulatingwater heating burner of the system shown by FIG. 1.

DETAILED DESCRIPTION (A) General Structure Under this heading, thegeneral structure of the heating system will firstbe briefly described.The operation of the system and the structural details necessary orrelating to such operation will be discussed under the heading (B)Operation.

Referring now to the drawings in greater detail, and to FIG. 1 inparticular, a heating system 10 according to the invention includes agas circuit 12, indicated by tailed arrows, and a water circuit I4,indicated by the nontailed arrows, such designation of the gas and watercircuits being employed throughout the drawings. In the former circuit,gas flows from a regulated pressure source 16, through a gas flowcontrol valve 18, (shown in greater detail in FIG. 4), through thegaslift pump 20 (shown in greater detail in FIG. 6) and then to themodulated burner 22 (shown in greater detail in FIG. 8), the combustionproducts being discharged to atmosphere through the usual stack 24. Inthe water circuit 14, the pump 20circulates water heated in theburner-boiler 22 to theradiators 26 in the heated zone 28 and back tothe burner-boiler 22.

Referring now to FIG. 2, the gas from the main (not shown) entersconduit 30, which may have manual valves 32 positioned on both sides ofany suitable gas pressure regulating valve 34. The conduit 30 alsoincludes a gas flow control valve 18, which, as shown in FIG. 4, maycomprise a conduit section 36 having an elastomeric sleeve 38 suitablymounted therein. The ends 40 of sleeve 38 may be rolled over the ends ofthe section 36, for example, and retained by means of rings 42 threadedon the ends 44 of the conduit 30. Any suitable means may be provided tocompress the elastomeric sleeve 38 to provide a gastight seal, and, inthe FIG. 4 structure, this is accomplished by the rings 42 drawing theconduit ends 44 axially toward the section 36 to compress the rolledsleeve ends therebetween. The rings 42 may be restrained axially by theannular beveled flange 46 on the section 36, and sealing compound,soldering or other known specific means may be employed to enhance thesealing.

The variable volume 48 between the elastic sleeve 38 and the rigidsection 36 communicates through a standpipe 50 with a reservoir 52containing a float valve 54 for at times closingthe port 56 at the topof the reservoir so that the heavy liquid 58 contained therein and inthe standpipe 50 and the variable volume 48, for a purpose tobedescribed under Operation, cannot rise beyond the port 56. A hollowbellows assembly 35 having an opening 37 at its upper end may bethreaded or otherwise sealably secured into the section 36, the bellowsbeing adjustable axially by a screw 39 carried by a bracket 41 securedto the section 36, whereby liquid 58 within the bellows 35 may be, forexample, forced out to increase the height of the column 58 for controlpurposes.

Referring now to FIGS. I3 and 5, the zone or space to be heated 28, suchas a room of a residence, may include a window 60 or other surface, andthe room temperature rapidly decreases, during the heating season, asthe window 60 is approached. A hollow pressure bulb 62 is mounted on thewall 64 adjacent the window 60 on a pivot mechanism 66 and connected byany suitable gastight means to a small conduit 68, which may be disposedin the wall 64 and is connected by gastight means to the reservoir 52 atport 56. The bulb 62 and the conduit 68 contain a gas and/or liquid 70that is not miscible with the heavy liquid 58 contained in the reservoir52, and whose vapor pressure varies substantially with temperaturevariations at the bulb which may be pivoted closer to the window whenadditional heat or a higher temperature is desired, and vice versa, asshown by the arrow 72.

While the operation of the system is described below, it will beapparent at this point that increased temperature at and pressure in thebulb 62 forces the heavy liquid level downwardly in the reservoir 52 andcauses the liquid 58 to constrict the elastic sleeve 38 and thus reducethe gas flow area therethrough. The converse is also true because theelastomeric sleeve 38 opposes such constriction and tends to retain amaximum flow area.

Referring now to FIG. 6, any gas passing through the sleeve 38 flowsfrom conduit 30 into the innermost vertical tube 74 of the gas-lift pump20, which further comprises an outer pipe or tube 76, which is closed atthe bottom and the open upper end 78 of which extends into the waterreservoir 80 and has formed on or attached thereto a conical ring 82 fora purpose to be described. Water 84 in the reservoir is replenished fromthe usual supply conduit 86, and a float valve 88, which is shown onlyschematically and may include any well-known levered structure adequateto close conduit against the water pressure therein, maintains the waterat any desired level, as at the level 90. The water leaves the reservoirby way of conduit 92, and it enters the pump 20 at the bottom throughconduit 94.

' An intermediate constant submergence tube 96, open at its bottom andclosed at its top, is fitted with clearance over the inner tube 74 so asto receive gas therefrom, and it preferably may have secured at itsbottom end a plate 98 having small openings 100 therein for a purpose tobe described. The inverted intermediate tube 96, which is filled withgas, thus floats in the water contained in the outer tube 76, and it mayrise into the tube 102 extending from the top of the water reservoir 80.Gas thus flows from the inner tube 74 into the inverted tube 96,downwardly through the clearance 104 between the inner and the invertedtube, through the perforated plate 98, up through the water in theclearance 106 between the inverted tube and the outer tube, into thevolume 108 in the water reservoir 80 above the water level, up the tube102 and out the conduit 110 leading to the burner-boiler 22. Pumping ofthe water is, of course, accomplished by the gas rising and expanding inthe outer tube.

As shown in FIG. 6, heated water pumped into the reservoir 80 iscirculated by gravity through conduit 92 to the radiators or other heatradiating devices 26, which may be in series or parallel connection, andthen to the burner-boiler 22 through conduit 112 for heating and returnthrough conduit94 to the bottom of the pump 20.

Reference is now made to FIG. 8, which is a substantially enlarged sideelevation, with portions thereof cutaway and in cross section, of theburner-boiler 22 shown in FIGS. 1 and 6. It will be understood thatexcept for the specific structural features to be described, theburner-boiler 22 may be of any desired construction.

The burner-boiler is formed to include a firebox 114 having a stack 24and surrounded to any desired extent by a water chamber or boiler 118having a cold water inlet, conduit 112, and a hot water outlet, conduit94. The burner 120 is formed with an inclined passage 122 connected tothe gas supply conduit 110 and having a series of burner nozzle risers124 of progressively increasing height extending upwardly therefrom. Thelower end of the inclined passage 122 is connected by the conduit 126 tothe bottom of the control tank 128, the upper end of which is connectedby conduit 129 to a venturi restriction 130 in the gas supply conduit110 and which contains a float valve 132 for sealing the conduit, and bya branch conduit 134 to a fluid reserve tank 136 that may be refilledthrough nonvented plug 138. I

The reserve tank 136 operates on the inverted container principle tomaintain the inclined passage 122 and'nozzles 124 filledwith a liquid140 to the level 142 only when gas flow is stopped; that is, the liquid140 will be replenished to the'intersection of conduit 134 with conduit126 whenever it drops below that level and when no gas is flowing. Whilethe nature and function of the liquid 140 will be described below, itshould be noted that increasing gas flow through the venturi restriction130 will cause a decreasing pressure in the control tank 128, thisincreasing pressure differential across the liquid 140 causing the level142 thereof to drop in the burner 120 and rise into the control tank128, thereby successively permitting additional nozzles 124 to flow gasinto the firebox.

(B) Operation Temperature Control of Heated Space and criticalobjectives of such a system. Since the combustion process is itselfmodulated without frequent recourse to the extremes of either ON or OFF,it is necessary that some specific temperature control range be selectedas representative of these two extremes. In this specific example, 72 F.has been selected to be normal, with provision that a temperature riseof 0.5 F. will completely stop the water pumping and gas combustionprocess, whereas a drop of 05 F. will cause combustion gas flow andpumping to be at design maximum, which in this case has been arbitrarilyselected to be 60,000 B.t.u. s/hr. input or one cubic foot of gas/min.for a typical single heated zone installation. This input capacity can,of course, be modified as necessary by the design engineer.

In other words, a control temperature range of l.0 F. should govern theentire gas-flow range from zero to the design maximum. In practice itwill be found that this is capable of holding the temperature of a givenheated space to within'plus or minus 0.05 F., provided, or course, thatthe total output capacity of the burner is equal to or in excess of themaximum heat loss that can be expected on the coldest and/or windiestday anticipated.

Beginning in the heated zone 28, the control system consists of a smallpressurized bulb 62 containing a suitable gas and/or fluid 70 andmounted on a pivot 66 that is attached to the wall or ceiling 64 so thatit can be moved into and out of slightly higher or lower temperatures,as, for example, close to the window 60 or other similarly cooler area,or away from such an area and into inherently warmer areas, includingpositions immediately above or close to the zone heat radiation devices.This is the only normal manual adjustment of temperature controlavailable in the system l0 for actuation within the heated spaceinvolved, but the liquid column in standpipe 50 (secondary heavy-liquidcontrol column to be discussed later) may be constructed so that it canalso be adjusted (screw 39 in FIG. 4), thereby offering two independentforms of manual control.

Using the single control, if an increase in temperature were desired,for example, the pressure bulb 6 2,would be moved closer to a window 60or other similarly cooler area, if a temperature decrease were desired,the bulb would be moved away from the cooler area into a normally warmerlocation. Since the temperature variation within only a few inches of awindow may be quite pronounced, it will be found that the required bulbmovement will usually be quite small. The bulb motion could, if desired,be calibrated to reflect simulated or actual temperature settings.

In order that the bulb 62 may be moved or swiveled in and out on itspivot, 66,it is necessary that a highly durable flexible tubing 69 or anabsolutely gastight swivel fitting 66 be provided for the connection ofthe bulb to the tubing 68 permanently installed and 'concealed withinthe walls 64. The tubing may be quite small, and ordinary one-sixteenthinch commercial copper tubing is adequate. The other end of the tubing68 connects with the top of a relatively small diameter verticalstandpipe or column 50 containing a predetermined static hea of somesuitable heavy liquid 58 with low vapor pressure characteristics andcompletely nonmiscible with the gas/liquid 70 used in the pressure bulb.The internal volume of the connecting tubing 68 should be small inrelation to the volume of the pressure bulb 62. Wherever it ispracticable to do so, the tubing 68 should be routed so as to not passthrough or near any hot areas as this can adversely affect uniformity ofcontrol, particularly if such areas are subject to considerabletemperature variations that do not necessarily parallel temperaturevariations within the heated zone. The column of heavy liquid'58communicates with and operates the flow valve 18 controlling gas flow,as shown in FIGS. 2 and 4. The height of the column of liquid 58 isinversely proportional to its specific gravity, Le, a fluid with onlyhalf as much specific gravity would require a column height or headtwice as high.

If Freon l l (CCl F) is used as the primary control gas/liquid 70, thenthe height of the secondary heavy liquid column 50 should be such thatwhen a vacuum of exactly 0.575 p.s.i.g. (when atmospheric pressure isstandard or 14.7 p.s.i.a.) or an absolute pressure of 14.125 p.s.i.a.(when atmospheric pressure-is standard) exists in conduit 68 connectedto the top of the. column, the weight of the liquid 58 is justsufficient to completely constrict the sleeve 38 and stop all gas flowagainst the regulated input gas pressure in conduit 30. Further, thecross-sectional area and the volume above the liquid column 58 should besuch that all or most of the heavy liquid 58 is withdrawn from the gasflow control valve chamber 48, so as to permit maximum gas flow, whenthe 'vacuum is increased to 0.865 p.s.i.g. or to an absolute pressure of13.835 when atmospheric pressure is 14.7 p.s.i.a.

Since these pressure values may be too critical for equipment andinstrumentation available to most installation personnel, this problemcan be greatly simplified by merely using a transparent tubing 50 forthe vertical column and affixing thereto,- or inscribing thereon,specific levels to which the liquid 58 should be initially filled,together with an indication as to the exact amount of liquid that shouldbe added after the 1 action of valve 18 has been checked to insurecomplete constriction of sleeve 38 and gas flow stoppage when the upperend of the column 58 is open to the atmosphere prior to its beingconnected to the control gas/liquid, in bulb 62 and conduit 68. 7

Additional desirable fine adjustment is made possible by the screw 39 tovary, within design limits, the height of the heavy liquid column. itshould be noted here that a normal heated zone temperature of 72 F. willgive Freon 1 l a pressure of approximately l3.98 p.s.i.a, or about 0.72p.s.i.g. below atmospheric pressure, and that this reduced pressure willtend to reduce the sleeve constricting pressure in the gas flow controlvalve 18 by an equal amount.

The elastomeric sleeve 38 in the gas flow control valve 18 should be onethat is completely impermeable and totally unaffected by the gas usedfor combustion or by the control liquid 58 used in the vertical column.it should also possess good elastic recovery properties, along with verylittle tendency to acquire a permanent set. Such requirements narrow thefield somewhat so as to eliminate almost all known elastomers with theexception of certain of the silicones and polyurethanes. The elastomericsleeve 38 should be assembled or installed with sufficient initialstretch so as to be capable of expulging all of the control liquid 58from the valved chamber 48 without any assistance from gas pressurewithin the sleeve, and with the heavy liquid control column 50disconnected.

it will thus be apparent that a combination of three forces tends tomaximize combustion gas flow. These forces are (a) the elastic recoverycapabilities of the elastomeric sleeve 38 in the gas flow control valve18, (b) combustion gas pressure itself and (c) the absence of pressureor partial vacuum in the primary gas/liquid (bulb 62) control system.The latter force amounts to 0.29 pound per square inch (0.29 p.s.i.) forthe entire 1 F. operating range, plus an additional 0.575 p.s.i. toaccount for the reduction below atmospheric pressure when Freon l 1 isat 72.5 F. which is the upper limit of the control range.

It is further apparent that the incoming combustion gas pressure is, byfar, the largest of the forces involved. In designing the heating system10, certain realistic values should first be assumed for the purpose ofmaking a trial computation. Thus, let it be assumed that the inputcombustion gas pressure is p.s.i,g., that the primary gas/liquid controlpressure variation (over 72.5-72.5) is 0.29 p.s.i.g. and that theelastic recovery forces in the gas flow control sleeve 38, whentranslated into the hydraulic pressures generated by the secondary heavyliquid column 58, are 0.39 p.s.i.g. when the sleeve is so asto permitmaximum combustion gas flow. This establishes the two extreme criticalpressures on the hydraulic side of the elastomeric sleeve 38, i.e. 5.39p.s.i.g. when combustion gas flow is stopped, and 5.1 p.s.i. g. when gasflow is at a maximum.

The above 0.29 p.s.i.g. differential (5.39-5 .1) corresponds to theworking pressure variation in the primary gas/liquid pressure controlsystem. It means that the height of the heavy liquid 58 in the secondarypressure control system acting to constri ct the combustion gas controlvalve sleeve should be such as to produce a pressure-of 5.39 p.s.i.g.plus 0.575 p.s.i.g. additional to compensate for the pressure reductionin Freon 11 when it is at 72.5 F., or a total of 5.965 p.s.i.g. actingon the sleeve when the top of the secondary pressure control column isopen to atmospheric pressure. If this liquid were water (notrecommended), the height of the filled portion of the column 50 shouldbe 5.965X2.3 l=l3.779l5 or approx.

l 3.78 feet.

The volume of the reservoir 52 should be sufficient to accommodate allof the liquid 58 within the control sleeve 38 when the conduit 68 isconnected to the reservoir and the primary gas/liquid control pressuretherein is a vacuum of 0.865 p.s.i.g. or more. A float-type check valve54 should-be provided in the reservoir 52, or at the top of thesecondary pressure control system, so as to prevent any of the heavysecondary control liquid from overflowing back into the primary systemwhen the primary control pressure is more than 0.865 p.s.i.g. belowatmospheric pressure. If no such check valve were provided, suchoverflow back into the primary system could happen, for example, if theheating plant were to be shut down so that there is no combustion gaspressure acting on the sleeve 38 and the normally heated zone where theprimary pressure control bulb 62 is located might become quite cold.

Should a given sleeve construction and elastomeric composition be foundto require too much pressure for actuation under optimum conditions, itmay be stretched more tightly by lengthening the tube 36 on which it ismounted, and the liquid withdrawal volume above the hydraulic fill linein the secondary pressure control system should be increasedaccordingly. It is preferable that this withdrawal volume be asubstantially enlarged section of the secondary pressure control tubing,like the reservoir 52, so as to provide room for the check valve float,and to reduce the overall height requirements for withdrawal.

The overall height requirements may be further reduced by using aliquid'heavier than water, or water containing some soluble materialsuch as calcium chloride, whereby the specific gravity may be increasedto about 1.54 in a saturated solution. In the earlier example wherewater required an initial fill height of some 13.78 ft., this can bereduced to 5.965

-2.31/l.54=8. 9 7475, or approx. 8.95 ft. However, the use of Gas-LiftForced-Circulation Water Pump As previously stated, theforced-circulation water pump 20 operates on the gas-lift principle,using the pressure already available in the combustion gas. Combustiongas passing through the flow control valve 18 is made to enter the baseof a vertical water pumping tubelike apparatus 20, the diameter of theouter tube 76 being greatly exaggerated in size in the drawings forclarity. The gas then passes upwardly through the smaller tube 74 whichterminates at some intermediate height which will be more accuratelydefined. The inverted tube 96 encloses the first tube 74, and it servesthe function of causing combustion gas to be discharged into thecirculating water at some predetermined constant submergence depth. Thisis necessary in order to maximize water volumetric flow, since the gaspressure required to start the pumping operation from some givensubmergence depth is greater than the pressure required to keep thepumping action going once it is started.

casing 76 and the gas filled constant submergence tube 96 will, when nogas is'flowing, normally be very near the top of the main casing 76,about midway in the overflow tank or water reservoir 80, as at 90. Thecone at the top of outer tube 76 is provided to prevent the noise offalling water.

When pumping action begins, the small gas bubbles, formed in part by theapertured plate 98 attached to the open bottom end of tube 96,intermingle with the water so that the combined weight of the water andmixture above the bottom of the constant submergence tube will beconsiderably less than it would be if the gas bubbles were not present.Since the constant submergence tube floats in this water, it cannotfloat as high when the weight of the flotation water is reduced byintermixed gas bubbles, and consequently it sinks to a lower level. Thenet effect is to insure that the gas will always exit from the base ofthe constant submergence tube at or very near the design operating gaspressure as controlled by the automatic pressure reduction valve 34. Asa specific example, if the operating combustion gas pressure isp.s.i.g., then the distance from the normal static water level 90, whenno gas is flowing, to the bottom of the constant submergence tube aplate 98 should be just under 5 2.3 l=l 1.55 ft. In other words, theconstant submergence tube 96 should be ballasted to float submerged tothis depth.

To'maximize efficiency, the constant submergence tube 96 should betapered so that its diameter is slightly smaller at the top, or theouter casing 76 should be similarly but oppositely tapered so that itsdiameter is slightly larger at the top. The amount of this taper is muchtoo small to be shown in the drawings; however, it can be calculated onthe basis that the cross-sectional area at any elevation of thegas-water flow should be equal to the combined volumes of gas and waterat that elevation, it being clear that the rising gas is constantlyexpandin'gbecause its submergence depth is steadily decreasing. Thesmallest cross-sectional area for the gas-water mixture should be, insquare inches, equal to the gallons of water flow/min. divided by 12.

Pumping will be more efficient if the water is raised at a steadyuniform flow rate rather than at a continuously accelerated rate, and auniform flow rate can be attained by incorporating a suitable expansiontaper into the design. The efficiency is further enhanced by attachingthe finely perforated plate 98 to the bottom of the constant submergencetube 96 to divide the gas into smaller bubbles because larger bubblesoffer a somewhat lesser amount of total surface area for contact orcohesion with the water. i

. The amount of water than can be pumped by this gas-lift method isdependent upon many variables, not the least of which is the totalresistance to flow offered by the radiation system and its connectingpiping to and from the boiler room. his. essential that the hydrostatichead or pressure of the water pumped be such as to overcome this flowresistance to the extent that the return water flow to and through theboiler 22 and then to the base of the gas-lift pumping assembly 20 willbe at a rate sufficient to replace the water in the gas-lift columnwithin outer pipe 76 without an excessive amount of fpulldown" on theconstant submergence tube. Should tube 96 bottom," it is clear that thecombustion gas could exhaust from its base at a much higher rate becauseof the reduced resistance resulting from a decrease in the effectiveweight of the overlying water, and as a consequence the amount of wateractually circulated would be reduced.

The total volumetric water flow required is primarily related to theheat input to the boiler 22, and secondly to the heat output through theradiation system. On the input side, 1 cu. ft./min. or 1,000B.t.u.s/min. was previously hypothetically assumed as an operatingmaximum for a typical single heating zone installation. If the boiler 22is 80 percent efiicient, then 7 some 800 B.t.u.'s/min, will enter thewater. If the boiler contained only 8 lbs. or just slightly under 1 gal.of water, the temperature of this 8 lbs. of water would be raised 100 F.say from 100 F. to 200 F, and it would be necessary that this Stated inanother way, the water level between the main pump water be replacedonce/minute, i.e., the required minimum water circulation would beapprox. 1 gaL/min. This situation would, of course, also require thatthe radiation system be capable of losing 800 B.t.u.s/min., but it mightbe extremely difficult or impracticable to distribute or spread out only8 lbs. of water over a large enough area as to be able to lose 800B.t.u.s/hr.lt is therefore preferable that the volume of water pumped begreater than 8 lbs/min.

Fortunately, the gas-lift system is capable of pumping considerably morewater, just how much more depending upon several factors, including thetotal lift height. The maximum lift height is limited by the effectivegas pressure. In the construction of the proposed system 10, it can beseen that there is an overpressure" imposed upon the water pumpingsystem which is greater than atmospheric pressure, but less than the sumof atmospheric pressure plus the incoming gas pressure, the amount ofthis overpressure depending upon the rate of gas flow through the burner120. That is, if the gas flow is restricted only a small amount, thenthe overpressure" will be relatively low. If the burner orifices 124 aresubstantially the same as those presently used in the so-calledlow-pressure systems, i.e., for operation at about 0.25 p.s.i.g, and ifthe pressure drop due to friction in the pipes leading from the top ofthe water pump 20 to the burner 120 is another 0.25 p.s.i.g, then theoverpressure could be approximately 0.5 p.s.i.g. If the incoming gas isat 5 p.s.i.g., and if the pumping system were percent efficient, then 1cu. ft. of gas/min. at 5 p.s.i.g. could lift 1 cu. ft. of water adistance of 2.3 lX(50.5 l0.395 or approx. 10% ft. Since such systems areonly about 50 percent efficient, the amount of water would be halved sothat 1 cu. ft. gas/min. at 5 p.s.i.g. would lift 7.48/2=3.74 gals/min.to a height of 10% ft. With an overpressure of 0.5 p.s.i.g., theconstant submergence tube 96 should be ballasted to float at a depth ofapprox. 10% ft. instead of the l 1.55 feet previously indicated.

This l0%ft. submergence depth also represents the effective pressurehead" for the circulation of water except that there is a small lossbecause of the need to insure that the water level in the overflow tankis always a few inches lower than the top of the pump outlet. Fourinches or one-third ft. should be adequate for this purpose, and thisleaves an effective pumping head of 10 ft. or l0/2.3 l=4.329 or about4.33 p.s.i.g. for water circulation, which should be adequate for most60,000 B.t.u./hr. single heated zone installations. I

It should be noted here that it is not essential that the incoming gaspressure be limited to only the 5 p.s.i.g. used in the precedinghypothetical installation, and many modern gas companies are alreadyequipped to supply gas at pressures up to 50 p.s.i.g. or more. it can beseen that if the incoming gas pressure were to be increased to 10p.s.i.g., for example, and if the burner construction and the pipefriction loss were the same, then the pressure available for watercirculation could be increased to 2.3l(l00.5)0.25=21.695 ft. or apressure of 2l.695/2.3l=(l9.39 p.s.i.g. (approx.) for circulation. Sucha pressure increase would, of course, require that the secondary (heavyliquid) pressure control system be approximately redesigned, togetherwith the substitution of an appropriate pressure reduction valve 34.

It should be noted here that as the water temperature increases, itdecreases in weight (to 8.039 lbs./gal. at 200 F.) and therefore liftseasier; at the same time, the pumping gas is expanded due to increasedtemperature so that its volume is increased substantially to furtherincrease the amount of water pumped.

Some water vapor is lost in this system because it mixes with thecombustion gas and enters the combustion chamber. This is more of anasset than a liability, however, because this substantially improvesthermal conductivity and heat transfer between the hot combustion gasesand the water chamber of the bumer-boiler 22, according to numerousresearchers, including several U.S. Government laboratories.

The heat gained by the combustion gas when passing through the pump 20is not lost since it is returned to the combustion chamber 114 if theconnecting lines are suitably insulated. In fact, the entire pumping,overflow tank, boiler, and

all associated lines should be properly insulated to minimize losses.

Automatically Self-Modulating Gas Burner Referring to FIG. 8, burner 120employs a high temperature, exceptionally low vapor pressure liquid 140having high cohesion and low adhesion properties as the modulationcontrol media. For-example, some of the high temperature siliconelubricants are well suited to this application. When the burner isinoperative, i.e., when no gas is flowing in conduit 110, the controlliquid 140 seeks the horizontally level position 142. The reserve tank136 provides replenishment fluid as required, even through the amount offluid expected to be consumed has been calculated to be extremely low,probably less than 0.01 gal./year for an average 60,000 B.t.u./hourinstallation. It will be noted that the temperature of liquid 140 isnever very high, in spite of its close proximity to the firebox 1 14,since the burner 120 is cooled by both the incoming gas and theair usedfor combustion. As state previously, certain 7 details of theburner-boiler 22 are of no significance to the invention, among thesebeing the combustion air supply, which is not shown except for the airjets represented at 125. Further, HO. 8 illustrates a sectional view ofa single row of burner nozzles 124, and it will be understood that theburner 120 could have any desired number of rows of nozzles 124, in avariety of configurations.

The reserve tank is of the inverted container" type so that the fluidlevel 142 in the burner control system will be held constant, and itwill be noted that filling can only occur when theburner 120 isinoperative and when the fluid level 142 is below the level of theconnection (conduit 134) to the reserve tank 136.

As shown in H6. 8, when combustion gas is flowing at a very slow rate,only the three burner nozzle 124 at the extreme left (FIG. 8) willignite (the pilot light for ignition is not shown) and be operative.Three nozzles are a purely arbitrary consideration, and only one or anynumber of nozzles may be used for the lowest operating condition justabove completely OFF. It will be recognized that the orifice size ofthese individual burner-nozzles 124 will large dictate the number to beactivated in the lowest heating condition.

Even when combustion gas flow is at a predetermined minimum, there willgenerally be enough pressure in the burner assembly 120 to cause thefluid 140 at the extreme left in passage 122 to depress slightly, whileconcurrently causing the fluid in all nozzles 124 except the first threeon the left to raise even less slightly since the fluid volume decreaseon the left will be distributed equally among all the other inactivefluid columns or nozzles 124 plus the control column in conduit 126 onthe extreme right.

As combustion gas flow is increased, its passage through the venturi 130in conduit 110 will tend to generate a gradually increasing vacuumtransmitted to the top of the control tank 128, which normally would beinsulated from the burnerboiler 22. As the vacuum increases, fluid 140is withdrawn from the burner 120 control assembly, until none remainswhen gas flow is at a design maximum. Thus, the venturi 130 should .beselected on the basis of its ability to lift all of the fluid 140 intothe control tank 128 until the last burner orifice 124 at the extremeright is uncovered" and operating.

The float valve 132 in the control tank is for the purpose of providingsafety against the possibility that gas flow might in some mannerinadvertently exceed the design maximum, and thus tend to pull thecontrol liquid 140 up and over into the venturi. This could do no realdamage, of course, since the fluid 140 would merely fall back downthrough the gas inlet conduit 110. However, there is some possibilitythat a condition could exist wherein the reserve tank 136 might becaused to overfill the system, and this could either cause the entireburner assembly 120 to shut down or cause some of the liquid' to passupwardly through the nozzles and spill over into the combustion airinlet openings 125. The float valve is therefore considered to bereasonably essential. It should be noted here that the volume of thecontrol tank 128 with the float 132 against its seat 127 should be equalto the volume of fluid required to fill the burner control assembly fromthe bottom of the standpipe conduit 126 to the design fluid level 142when no or minimum gas is flowing. To allow for normal manufacturingvariations, this volumetric relationship may be finely adjusted at thetime of installation by moving the float valve seat 127 up or down, orby the addition or removal of spacer washers (not shown) as necessary.

It will be apparent from the above description, wherein the inventionhas been disclosed in such clear and concise terms as to allow thoseskilled in the art to practice the same, that the invention provides anautomatic, self-modulating, gasfired, gas-powered, forced-circulationhot water heating system that, requires no electrical power and ischaracterized by the numerous initially stated objectives, as well vasproviding other advantageous results.

While the invention has, been shown and described as embodied in a hotwater heating system, certain portions thereof are applicable to anysystem, such as a forced air system, as well as for other uses.

To those skilled in the art to which this invention relates, manyvariations in construction and widely differing embodiments of theinvention will suggest themselves without departing from the spirit andscope of the invention. Thus, the disclosures and description herein arepurely illustrative and are not intended to be in any sense limiting.

I claim:

1. A fuel burner for burning a fluid fuel, comprising a burner housing,a plurality of burner nozzles, conduit means formed in said housing, aplurality of passage means communicating between said conduit means andsaid burner nozzles, an inlet for admitting a flow of said fuel to saidconduit means, liquid valving means received in said conduit means andflowably moveable to varying levels for both completing and terminatingcommunication between one or more of said plurality of passage means andsaid conduit means, means for creating a pressure differential directlyrelated to the volume rate of flow of said fluid fuel to said conduitmeans, and additional means for applying said pressure differential tosaid liquid .valving means in orderto thereby vary the level of saidliquid for both completing and terminating the flow of said fluid fuelfrom said conduit meansto one or more of said plurality of nozzles.

2. A fuel burner according to claim 1, wherein said fluid fuel comprisesa gas under pressure.

3. A fuel burner for burning a fluid fuel, comprising a burner housing,a plurality of burner nozzles, conduit means formed in said housingcommunicating with said burner nozzles, an inlet for admitting a flow ofsaid fluid fuel to said conduit means, means responsive to the volumerate of flow of said fluid fuel to said conduit means for bothcompleting and terminating the flow of said fluid fuel to one or more ofsaid plurality of burner nozzles, said conduit means comprising aninclined passage with an upper disposed end and a lower disposed end,said upper end being in communication with said inlet, said lower end ofsaid inclined passage being operatively connected to a control chamber,said means responsive to the volume rate of flow of said fluid fuelcomprising a venturi for sensing the rate of flow of fluid fuel to saidinclined passage, second conduit means having a first end effectivelyexposed to the pressure within said venturi and communicating at itsother end with said control chamber, a plurality of branch passagesleading from said inclined passage to said burner nozzles, and a liquidfilling said inclined passage and said branch passages to a commonvariable level so as to block the flow of said fluid fuel to saidnozzles, said level being determined at least in part upon the rate offlow of said fluid fuel through said venturi as indicated by saidpressure within said venturi and communicated to said control chambervia said second conduit means.

4. A fuel burner for burning a fluid fuel, comprising a formed in saidhousing communicating with said burner nozzles, an inlet for admitting aflow of said fluid fuel to said conduit means, means responsive to thevolume rate of flow of said fluid fuel to said conduit means for bothcompleting and terminating the flow of said fluid fuel to one or more ofsaid plurality of burner nozzles, said conduit means comprising aninclined passage with an upper disposed end and a lower disposed end,said upper end of said inclined passage being in communication with saidinlet and said lower end being connected to a control chamber and to aliquid supply tank, a fluid flow gauging restriction in circuit withsaid inlet and said upper end, said gauging restriction being effectiveto produce a variable pressure of a magnitude related to the rate offlow of said fluid fuel through said restriction, and second conduitmeans communicating between a source of said variable pressure and saidcontrol chamber said second conduit means being effective to communicateto said control chamber said variable pressure corresponding to the rateof flow of said fluid fuel through said gauging restriction and to saidinclined passage, said inclined passage including individual upwardlyextending branch passages of progressively increasing lengthrespectively feeding said nozzles, said branch passages being filledwith said liquid to a predetermined level whereby at least one of saidbranch passages is uncovered thereby at a minimum rate of flow of saidfluid fuel, the total pressure of said fluid fuel at the upper end ofsaid inclined passage applied to the exposed surface of said liquid andsaid variable pressure being, applied to said control chamber and liquidsupply tank being effective to cause said liquid within said inclinedpassage to flow into said tank and progressively uncoveradditionalbranch passages in accordance with the rate of flow of said fluid fuelthrough said gauging restriction.

5. A fuel burner for burning a fluid fuel, comprising a burner housing,a plurality of burner nozzles, conduit means formed in said housingcommunicating with said burner nozzles, an inlet for admitting a flow ofsaid fluid fuel to said conduit means, means responsive to the volumerate of flow of said fluid fuel to said conduit'means for bothcompleting and terminating the flow of said fluid fuel to one or more ofsaid plurality of burner nozzles, said conduit means comprising aninclined passage with an upper disposed end and a lower disposed end,said upper end being in communication with said inlet, said meansresponsive to the volume rate of flow of said fuel comprises a fluidflow gauging restriction situated as to have said fluid flowing to saidinlet also flow through said gauging restriction, a plurality of branchpassages leading from said inclined passage to said burner nozzles, anda liquid filling said inclined passage and said branch passages to acommon variable level so as to block the flow of said fluid fuel to saidnozzles, said level being determined at least in part upon the rate offlow of said fluid fuel through said gauging restriction as indicated bythe pressure of said fluid fuel at said gauging restriction andoperatively communicated to said lower disposed end of said inclinedpassage.

6. A fuel burner for burning a fluid fuel, comprising a burner housing,a plurality of burner nozzles, conduit means formed in said housingcommunicating with said burner nozzles, an inlet for admitting a flow ofsaid fluid fuel to said conduit means, means responsive to the volumerate of flow of said fluid fuel to said conduit means for bothcompleting and terminating the flow of said fluid fuel to one or more ofsaid plurality of burner nozzles, said conduit means comprising aninclined passage with an upper disposed end and a lower disposed end,said upper end of said inclined passage being in communication with saidinlet and said lower end being connected to a liquid standpipe means, afluid flow gauging restriction in circuit with said inlet and said upperend, said gauging restriction being effective to produce a variablepressure of a magnitude related to the rate of flow of said fluid fuelthrough said restriction but less than the magnitude of the totalpressure of said fluid fuel, second conduit means communicating betweena source of said variable pressure and said liquid standpipe means, saidsecond conduit means being effective to communicate to said standpipemeans and to the exposed surface of said liquid within said standpipemeans said variable pressure corresponding to the rate of flow of saidfluid flow through said gauging restriction and to said inclinedpassage, said inclined passage including individual upwardly extendingbranch passages spaced from each other so as to progressivelycommunicate with said inclined passage at progressively varying heightsthereof, said branch passages respectively feeding said nozzles, andsaid branch passages and inclined passage being filled with said liquidto a predetermined level whereby a least one of said branch passages isuncovered thereby at a minimum rate of flow of said fluid fuel, thetotal pressure of said fluid fuel at the upper end of said inclinedpassage applied to the exposed surface of said liquid within saidinclined passage and said variable pressure being applied to saidexposed surface of said liquid within said standpipe means beingcollectively effective to cause said liquid within said inclined passageto flow into said standpipe means and thereby progressively uncoveradditional ones of said branch passages in accordance with the rate offlow of said fluid fuel through said gauging restriction.

1. A fuel burner for burning a fluid fuel, comprising a burner housing,a plurality of burner nozzles, conduit means formed in said housing, aplurality of passage means communicating between said conduit means andsaid burner nozzles, an inlet for admitting a flow of said fuel to saidconduit means, liquid valving means received in said conduit means andflowably moveable to varying levels for both completing and terminatingcommunication between one or more of said plurality of passage means andsaid conduit means, means for creating a pressure differential directlyrelated to the volume rate of flow of said fluid fuel to said conduitmeans, and additional means for applying said pressure differential tosaid liquid valving means in order to thereby vary the level of saidliquid for both completing and terminating the flow of said fluid fuelfrom said conduit means to one or more of said plurality of nozzles. 2.A fuel burner according to claim 1, wherein said fluid fuel comprises agas under pressure.
 3. A fuel burner for burning a fluid fuel,comprising a burner housing, a plurality of burner nozzles, conduitmeans formed in said housing communicating with said burner nozzles, aninlet for admitting a flow of said fluid fuel to said conduit means,means responsive to the volume rate of flow of said fluid fuel to saidconduit means for both completing and terminating the flow of said fluidfuel to one or more of said plurality of burner nozzles, said conduitmeans comprising an inclined passage with an upper disposed end and alower disposed end, said upper end being in communication with saidinlet, said lower end of said inclined passage being operativelyconnected to a control chamber, said means responsive to the volume rateof flow of said fluid fuel comprising a venturi for sensing the rate offlow of fluid fuel to said inclined passage, second conduit means havinga first end effectively exposed to the pressure within said venturi andcommunicating at its other end with said control chamber, a plurality ofbranch passages leading from said inclined passage to said burnernozzles, and a liquid filling said inclined passage and said branchpassages to a common variable level so as to block the flow of saidfluid fuel to said nozzles, said level being determined at least in partupon the rate of flow of said fluid fuel through said venturi asindicated by said pressure within said venturi and communicated to saidcontrol chamber via said second conduit means.
 4. A fuel burner forburning a fluid fuel, comprising a burner housing, a plurality of burnernozzles, conduit means formed in said housing communicating with saidburner nozzles, an inlet for admitting a flow of said fluid fuel to saidconduit means, means responsive to the volume rate of flow of said fluidfuel to said conduit means for both completing and terminating the flowof said fluid fuel to one or more of said plurality of burner nozzles,said conduit means comprising an inclined passage with an upper disposedend and a lower disposed end, said upper end of said inclined passagebeing in communication with said inlet and said lower end beingconnected to a control chamber and to a liquid supply tank, a fluid flowgauging restriction in circuit with said inlet and said upper end, saidgauging restriction being effective to produce a variable pressure of amagnitude related to the rate of flow of said fluid fuel through saidrestriction, and second conduit means communicating between a source ofsaid variable pressure and said control chamber said second conduitmeans being effective to communicate to said control chamber saidvariable pressure corresponding to the rate of flow of said fluid fuelthrough said gauging restriction and to said inclined passage, saidinclined passage including individual upwardly extending branch passagesof progressively increasing length respectively feeding said nozzles,said branch passages being filled with said liquid to a predeterminedlevel whereby at least one of said branch passages is uncovered therebyat a minimum rate of flow of said fluid fuel, the total pressure of saidfluid fuel at the upper end of said inclined passage applied to theexposed surface of said liquid and said variable pressure being appliedto said control chamber and liquid supply tank being effective to causesaid liquid within said inclined passage to flow into said tank andprogressively uncover additional branch passages in accordance with therate of flow of said fluid fuel through said gauging restriction.
 5. Afuel burner for burning a fluid fuel, comprising a burner housing, aplurality of burner nozzles, conduit means formed in said housingcommunicating with said burner nozzles, an inlet for admitting a flow ofsaid fluid fuel to said conduit means, means responsive to the volumerate of flow of said fluid fuel to said conduit means for bothcompleting and terminating the flow of said fluid fuel to one or more ofsaid plurality of burner nozzles, said conduit means comprising aninclined passage with an upper disposed end and a lower disposed end,said upper end being in communication with said inlet, said meansresponsive to the volume rate of flow of said fuel comprises a fluidflow gauging restriction situated as to have said fluid flowing to saidinlet also flow through said gauging restriction, a plurality of branchpassages leading from said inclined passage to said burner nozzles, anda liquid filling said inclined passage and said branch passages to acommon variable level so as to block the flow of said fluid fuel to saidnozzles, said level being determined at least in part upon the rate offlow of said fluid fuel through said gauging restriction as indicated bythe pressure of said fluid fuel at said gauging restriction andoperatively communicated to said lower disposed end of said inclinedpassage.
 6. A fuel burner for burning a fluid fuel, comprising a burnerhousing, a plurality of burner nozzles, conduit means formed in saidhousing communicating with said burner nozzles, an inlet for admitting aflow of said fluid fuel to said conduit means, means responsive to thevolume rate of flow of said fluid fuel to said conduit means for bothcompleting and terminating the flow of said fluid fuel to one or more ofsaid plurality of burner nozzles, said conduit means comprising aninclined passage with an upper disposed end and a lower disposed end,said upper end of said inclined passage being in communication with saidinlet and said lowEr end being connected to a liquid standpipe means, afluid flow gauging restriction in circuit with said inlet and said upperend, said gauging restriction being effective to produce a variablepressure of a magnitude related to the rate of flow of said fluid fuelthrough said restriction but less than the magnitude of the totalpressure of said fluid fuel, second conduit means communicating betweena source of said variable pressure and said liquid standpipe means, saidsecond conduit means being effective to communicate to said standpipemeans and to the exposed surface of said liquid within said standpipemeans said variable pressure corresponding to the rate of flow of saidfluid flow through said gauging restriction and to said inclinedpassage, said inclined passage including individual upwardly extendingbranch passages spaced from each other so as to progressivelycommunicate with said inclined passage at progressively varying heightsthereof, said branch passages respectively feeding said nozzles, andsaid branch passages and inclined passage being filled with said liquidto a predetermined level whereby a least one of said branch passages isuncovered thereby at a minimum rate of flow of said fluid fuel, thetotal pressure of said fluid fuel at the upper end of said inclinedpassage applied to the exposed surface of said liquid within saidinclined passage and said variable pressure being applied to saidexposed surface of said liquid within said standpipe means beingcollectively effective to cause said liquid within said inclined passageto flow into said standpipe means and thereby progressively uncoveradditional ones of said branch passages in accordance with the rate offlow of said fluid fuel through said gauging restriction.